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alphapointe
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join:2002-02-10
Columbia, MO
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·Socket Internet ..

EPM Power Meter Board ID

I'm hoping someone knows what I'm looking at here... this board (there are two of them) is connected to a set of shunts on our main electrical switchboard, and connected to the rest of our abandoned-in-place "energy management system" that the manager said never worked right. He can't find any documentation, and I don't even know who made it... I want to be able to read our current usage and integrate it with my own system. Does anyone know what this board is and maybe how to read from it? My DA boards each have 3 analog inputs that want 0-10v, which I guess is pretty standard in the industrial controls world.

(Sorry for the quality, all I had was my cell phone)


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leibold
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You really do need a better quality picture so that the component labels can be properly read.

A key component is certainly the "8-bit A/D converter with differential inputs" ADC0804 next to the potentiometer (probably adjusting the analog reference voltage for the A/D converter).

I would be very surprised if the 8 bit digital output of the A/D converter isn't directly connected to the "Asynchroneous Receiver/Transmitter Remote Controller" MM54240 since it too has an 8-bit bus interface and is located nearby on the board. The switch block next to the MM54240 is probably used to select the address on the serial bus when the chip is in slave mode.

Most of the remaining logic chips are from the CMOS 4000 series. I noted that many of them are analog multiplexers (4051, 4052, 4053) presumably switching different analog signals (voltage from the shunts you mentioned?) to the input of the ADC0804 A/D converter.

Overall guess: allow remote reading of multiple analog values (currents, voltages ?) with 8 bit precision.
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SparkChaser
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Downingtown, PA
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reply to alphapointe

The PCB looks hand drawn or am I missing something. Not even taped. A one of a kind thing.



shdesigns
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join:2000-12-01
Stone Mountain, GA

1 recommendation

Yes, non-plated through also.



alphapointe
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Columbia, MO
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reply to alphapointe

I'll get the good camera and go take a couple more pictures.
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leibold
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reply to SparkChaser

Not unusual for boards of that age (I'm guessing manufacturing date for that board late 1983 or probably 1984 based on the component date codes).

That doesn't have to mean one-off. It was probably drawn on transparencies that could be reused to photo-etch (using UV light) more then one pcb.
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mackey
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reply to alphapointe

You're probably better off looking up what the other end of the cable connects to

/M



leibold
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said by mackey:

You're probably better off looking up what the other end of the cable connects to

Guess: another MM54240 (in master mode) and a 8-bit processor
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alphapointe
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reply to alphapointe



208V Side (I can't get the shunt box open)



208V Board



480V Side



408V Board



408V Shunt
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alphapointe
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reply to mackey

said by mackey:

You're probably better off looking up what the other end of the cable connects to

/M

At the other end of the cable is a big box with a bunch more unlabled, undocumented boards...

Why the hell can't people document what the hell something does? How hard is that?
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mackey
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reply to leibold

said by leibold:

said by mackey:

You're probably better off looking up what the other end of the cable connects to

Guess: another MM54240 (in master mode) and a 8-bit processor

I meant the other end of the 8 power wires

/M


mackey
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reply to alphapointe

said by alphapointe:

At the other end of the cable is a big box with a bunch more unlabled, undocumented boards...

Why the hell can't people document what the hell something does? How hard is that?

Because that is "proprietary information" and they want you to instead hire their $$$$$$expensive$$$$$$ custom services.

Seriously, you can't even get IR remote control codes out of some of the TV makers

Without deciphering exactly what those chips/boards do, it looks like there are 3 CT's and 3 VT's... You'll probably need to get the specs off the actual transformers to find out what the max voltage is gonna be. In that 2nd to last pic, wire 8 and its resistors look extra crispy

/M


leibold
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reply to alphapointe

Given the look of the prior repairs and state of some of the capacitors as well as the overheated (burned out?) resistors I would say those remote monitoring boards were not designed for 480V

I can't fully figure out the wiring of the 480V shunt board. At first glance every terminal appears to be well grounded (not sure how old the installation is, but now it is definitely a code violation to use green wires for hot conductors).

The screw terminals on the top are for 3 phase supply and load while the screw terminals at the bottom are the connection to the remote monitoring board. If these were plain resistive shunts (not isolated from the 480V side) then the bridging of the common wire #1 to the three shunts would short circuit the phases. Any idea whether the pcb is designed to provide inductive or capacitive coupling ?

The wide traces for the shunt itself can be seen through the pcb but it is not clear to me how the smaller sensor traces are connected.
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alphapointe
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I just finished showing these pictures to the manager and telling him to forget interfacing it to our current system (I don't feel like dieing...)

My guess is whoever installed this system 30 years ago didn't exactly know what they were doing...
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mackey
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reply to leibold

said by leibold:

The screw terminals on the top are for 3 phase supply and load while the screw terminals at the bottom are the connection to the remote monitoring board. If these were plain resistive shunts (not isolated from the 480V side) then the bridging of the common wire #1 to the three shunts would short circuit the phases. Any idea whether the pcb is designed to provide inductive or capacitive coupling ?

The wide traces for the shunt itself can be seen through the pcb but it is not clear to me how the smaller sensor traces are connected.

It looks to me that the wide traces are a U shape, and I'm guessing the "sense" trace makes a ring around that U. The low voltage board probably senses the voltage picked up by that ring.

/M


alphapointe
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That's a 1800A panelboard that "shunt" is attached to... I would think there has to be CT's behind there somewhere, as there's no way in hell those #14 wires are carrying the building load...

There's no way in HELL I'm opening that panel... if the inside is anything like the outside, it'd probably blow up if I looked at it crosseyed...
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leibold
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1 edit
reply to mackey

said by mackey:

It looks to me that the wide traces are a U shape, and I'm guessing the "sense" trace makes a ring around that U. The low voltage board probably senses the voltage picked up by that ring.

It would be nice to see the underside of both the shunt pcb and the remote monitor pcb to get a better understanding but your guess seems reasonable.

That leaves us with:

(first terminal block)
#1 common wire for current sensors
#2 phase 1 current
#3 phase 2 current
#4 phase 3 current

(second terminal block)
#5 common wire for voltage sensors (this green wire really is grounded)
#6 phase 1 voltage
#7 phase 2 voltage
#8 phase 3 voltage

The wire/terminal numbers are as seen on the 480V remote monitoring board. The third terminal block on the other side of the remote monitoring board has supply voltage and pulse-width modulated serial communication bus.

Edit: based on alphapointe See Profile's last post (while I was typing this reply) the shunt board and its wiring makes more sense. The actual isolation is taking place in current transformers elsewhere and the shunt board transforms the currents into a measurable voltage (as opposed to directly measuring the CT output voltage as is often done today).

This also explains why the voltage sensor wires (#6, #7 and #8) are not connected to the shunt board but go on to the main panel.
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alphapointe
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Sounds reasonable to me. I put a scope on each of the red wires in image 2 (208v board) and had about 117VAC from each to ground. I haven't scoped the CT lines yet, as I can't find my good probe with the hook yet.
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alphapointe
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OK, I found the good scope probe and probed the "CT" lines, and got nothin'. It's possible everything has been disconnected inside the panelboard when this system was taken out of service. Like I said, I'm not openin' it up to find out.
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UHF
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reply to alphapointe

said by alphapointe:

There's no way in HELL I'm opening that panel... if the inside is anything like the outside, it'd probably blow up if I looked at it crosseyed...

Good plan. I don't mess around with 480 3ph.


leibold
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reply to alphapointe

said by alphapointe:

OK, I found the good scope probe and probed the "CT" lines, and got nothin'.

The voltages on the CT lines are likely to be very small (perhaps even in the millivolt range).
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alphapointe
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I had the scope down to 10mv/div, and still had a flat line..., and this was at 7pm when everyone was home and doing stuff, so we should have had some decent current draw. I imagine it's been disconnected...
--
"When the hammer drops, the bullshit stops"